Among adolescents, substance abuse and delinquency are associated with multiple problematic outcomes, including risky sexual behavior, mental health problems, family conflict, academic disruption, and disordered adult functioning. The longitudinal course and relationship of these risk behaviors has been posited to differ by gender, although little research has investigated gender-specific trajectories of both substance abuse and delinquency and their relationship over time, using a community (rather than clinical or other high-need) sample. Co-occurrence of substance use disorders and delinquency is common, but research focused on the emergence and longitudinal course of these behaviors by gender during adolescence is scant. This study aims to fill knowledge gaps by exploring shared and gender-specific influences (individual, peer, family and neighborhood) on substance abuse, delinquency and their relationship over time. The specific aims of the project are: (1) To identify latent classes describing developmental trajectories of substance abuse and delinquency specific to boys and girls;(2) To identify and examine shared and gender-specific risk and protective factors associated with trajectories of substance abuse and delinquency in boys and girls;and (3) To investigate and compare longitudinal relationships between substance abuse and delinquency in boys and girls in terms of time order and changes in severity, accounting for relationships with predictors. The proposed project utilizes data from the Project on Human Development in Chicago Neighborhoods (PHDCN), following approximately 1,100 male and 1,100 female youth and their caregivers across multiple years during three waves. Demographic covariates, individual and family risk and protective factors, and peer and neighborhood risk factors will be included in models of adolescent behavior over time. Gender-specific analyses will examine girls and boys separately, to identify heterogeneous patterns of development of substance use and delinquency and relationships. Multilevel models will be estimated to adjust for clustering of data by neighborhood and longitudinally over time. Findings from this study can help inform evidence-based strategies for prevention and intervention of substance abuse and delinquency that are effective for boys and girls. PUBLIC HEALTH RELEVANCE: The proposed study will investigate gender differences and similarities in adolescent substance abuse and delinquency, over time. Findings from this study can help inform evidence-based strategies for prevention and intervention efforts to curb risk behavior in boys and girls.